1. Field of Invention
The present invention relates to audio processing. More particularly, the present invention relates to a dual mode audio controller.
2. Description of Related Art
Universal serial bus (USB) is well known in signal communication for transmitting data. Computer system and various peripheral devices have widely adopted the USB port for transmitting data. A USB audio device can be used for PC peripheral applications, such as USB VoIP (voice over internet protocol) or USB headphone set. After the USB audio device is connected to the USB host, it takes the role of PC sound card for audio signal input and output. Depending on the actually design and operation, the USB audio device can automatically replace the PC sound card. For USB VoIP application, users can have voice communication through internet. On the other side, digital music player, such as MP3 player, is often connected to the USB port of the computer system for downloading the music into the digital audio player where the music controller works as a USB storage function.
However, to have multiple-function application, the USB audio device in conventional design is composed of various devices, which are in separate operations. It causes higher system cost and may be not easy in operation. The operation has to be based on the computer system, to which the audio device is connected. How to improve the application, particularly in mobile manner, is one of the issues in consideration.